What to Do When There Is White Stuff on Rose Leaves
White downy hair or spots on rose leaves are common disease signals, which not only affect their ornamental value but also threaten the survival of the plants. This article systematically explains the scientific treatment plan for rose powdery mildew through three parts: pathological analysis, emergency measures, and maintenance essentials.
Pathological Analysis of Rose Powdery Mildew
Symptom Characteristics and Causes
The presence of white powdery substances on the leaf surface is a typical symptom of infection by the single-celled fungus. When the daytime temperature is between 20-25°C and humidity is greater than 70%, the fungal spores spread rapidly through the air. The incidence rate of potted roses in closed environments can reach over 80%.
Disease Development Stages
In the early stage, it appears as white spots, in the middle stage, it forms a downy mycelium layer, and in the later stage, it causes the leaves to curl and wither. The infection can spread in just 5-7 days, requiring timely intervention to break the transmission chain.
Four-Step Emergency Treatment for Rose White Spots
Physical Isolation Treatment
Remove the diseased leaves with pruning shears disinfected with alcohol, leaving 1cm of healthy tissue at the base. For severely infected plants, the entire branch should be pruned, and the cut ends should be coated with sulfur powder to form a protective layer.
Reconstruction of the Root System
Remove the blackened roots after taking the plant out of the pot and soak them in 50°C water for 15 minutes to kill the fungi. It is recommended to use a new matrix of peat: perlite in a ratio of 3:1, ensuring that the drainage porosity is greater than 35%.
Chemical Control Plan
Alternately spray 25% azoxystrobin suspension (1500 times liquid) and 40% flusilazole emulsion (3000 times liquid) once a week for three weeks. Applying the medicine in the early morning can increase the adherence rate of the liquid.
Rose Powdery Mildew Prevention System
Environmental Control Standards
Keep a distance of more than 30cm between plants to ensure good air circulation. Use drip irrigation technology to control humidity, keeping the leaf surface wet for less than 4 hours per day. Maintain a light intensity of 30,000-50,000 lux for optimal growth.
Biological Control Technology
Regularly apply Bacillus subtilis formulations, with 5g of bacterial powder diluted in water for each square meter. Beneficial bacteria can inhibit the reproduction of over 90% of pathogenic fungi, with a sustained effective period of up to 45 days.
Through a three-dimensional prevention and treatment strategy of precise diagnosis, systematic governance, and environmental control, the recurrence rate of rose powdery mildew can be effectively reduced to less than 5%. It is recommended to check the undersides of leaves monthly, detect issues early, and maintain the healthy growth of the plants.